Method and apparatus for pulverizing



L. DE MARKUS METHOD AND APPARATUS `FOR PULVERIZING 3 Sheets-Sheet 2 Filed March 1e, 192s Du, 23, l. 924.

L. DE MARKUS METHOD AND APPARATUS FOR PuLvERIzING Filed March 16, 1923 3 Sheets- Sheet 3 INVENTOR Patented ee.. 23, 124..

PATENT GFFICE.

LOUIS DE MARKUS, 0F MONTROSE, PENNSYLVANIA.

METHOD AND APPARATUS FOR PULVERIZING;

Application filed. March 16, 1923. Serial No. 625,506.

To all whom t may concer/rt."

Be it known that I, Louis Dn Marinus, a citizen of the United States, residing at Montrose, county of Allegheny, State of Pennsylvania, have invented a new and useful Improvement in Methods and Apparatus for Pulverizing, of which the following is a full, clear, and exact description.

This invention relatesto methods and apparatus for pulverizing and is particularly adapted for pulverizing coal in connection with powdered coal combustion systems.

My invention provides an apparatus 'of improved construction which may 'be used in connection with, and adjacent to, a combustion apparatus, or may be separated therefrom as desired. Heretofore, a great objection to pulverizing apparatus has been that the particles at different stages of grinding or reduction are not graded or separated according to their lineness. In order to reduce relatively large lumps it is necessary to use a coarse grinding mill. It is desirable, however, that such a mill should be rapidly cleared of small particles since their presence clogs the action of the mill and materially reduces its efficiency.

My invention provides for passing a conveying fluid through the pulverizing apparatus and for varying the velocity .of such fluid to effect a gradation of particles of the material being pulverized. As is well known, amoving fluid, as, for example, air, will 'carry particles up to' a certain mass dependent principally on the air velocity. By varying the velocity of the conveying fluid,

I effect a suitable gradati'on of the particles.l

- the chute 3 meets a deector 5. This dein a very efficient manner.

The invention also includes a free fluid path through the entire pulverizing apparatusv This insures a free passage for particles which have already been sulliciently reduced at 4any point in the apparatus and` they may be carried away Withouty being subjected to a further reducing action. n the reduction of coal or similar materials,

the breaking up of a large particle generally ,results in the production of smaller particles of'warying size. Many of these are as small as desired and my invention permits of immediately carrying these suliiciently reduced particles out of the apparatus, thereby avoiding clogging and materially increasing the capacity of the apparatus.

To reduce coal to the required ineness, it is generally necessary to remove the moisture.I In the present invention, the convey- 'ing fluid acts as a drier and, being in inthrough a pulverizing apparatus embodyingV my invention;

Figure 2 is a section on the line II-II of Figure l;A l Figure 3 is a perspective view 'of a portion of the apparatus;

Figure 4 is a view corresponding to Fig- Y ure l but showing a modified form of the invention, and

Figure 5 is a section on the line V-V of Figure 4.

In the embodiment of the invention illustrated in Figures 1 and Q, coal, Which has been previously crushed to the usual fineness before being subjected to the act-ion of apparatus of this character, is' conveyed by aspiral conveyor 2 to a chute 3 and into a fluid conduit 4. The coal as it drops down Hector aids the conveying fluid in carrying the coal into the apparatus.

The conveying fluid, which is preferably air, is fed through a header 6 into the conduit 4 and its quantity may be regulated by ya suit-able damper 7. A suitable heater 6 may be provided in the conduit 6 to prehear.

the incoming air when pulverizing'wet ma terial. `The mixture of coal and air enters a primary pulverizing mill 8. A feed ribbon 9 is preferably employed to carry the larger lumps into the apparatus and this ribbon may be extended as far as the chute 3 if necessary.

is preferably of a generally conical form.v

The mill 8 contains a quantityl of ballsA 10 of varying size. The outlet of the mill` 8 comprises an axial passagee11 containing helical ribbons12 which prevent egress of the balls 10 asthe millis rotated but al' low a free passage for the air and coal.

As the air and coal leave vthe passage 11 they strike a delector 13 which reverses their flow and directs them into a second reducing lnill 14 which surrounds the mill 8. This mill is provided with grinding balls 1.5 and is carried on suitable rollers 1G. The millmay be driven in any desired manner as by a ring gear 17 n'ieshing With a driving pinion (not shown). Th'e millS is supported within the mill 14 by spacers 8b, preferably at both ends. These spacers are preferably narrow to minimize obstruction of the passages.

At times it may be desirable to introduce auxiliary air at some point along the fluid path. For this purpose, I provide a conduit 18 leading from the header 6 and provided With a damper 19 for regulating the quantity of auxiliary air or for cutting it oill entirely as may be determined by such conditions as the moisture inthe coal or the,

quantity of coal being ground. The aux-A iliary air passes around the delector 13 and helps to carry the coal through the neck 20 of the drum 14.

The powdered coal leaves the apparatus through a conduit 21 and may be taken directly to a furnace to be consumed or tov Aa storage tank as desired.

A- fan 2,2 may be employed to provide a ing the delector 13 beyond the joint 2 3- between the neck 20 and the conduit 19. This construction provides an efiicient. air seal for the rotating joint and etfectually eliminatesall leakage at this point. A similar air sea-l may be provided for the joint 24if necessary,- .but the fan 22 will generally maintain a sub-atmospheric pressure at this point and obviate any necessity for such construction.

It will be' noted that the drumsof both the reducing mills are of varying cross-section. This results in a varying velocity of air through the mills and, as explained above, eiec'ts a suit/able gradation of lthe coalparticles.l The balls 10 and 15 are' also. ade-d in size, the drum 8 containing larger balls than those in; the drum 14.

There is, moreover, a gradation of ball sizes in each drum and the general tendency is for the heavier balls to remain at the larger portions of the /drum'yvhe'ie the impact is niost necessary forl reducing large lumps, the size of the balls decreasing as the drum diameter is reduced. This results in an 'efl licient graded pulverizing system starting out With large balls and a large diameter drum and terminating in small balls and a smaller drum size. prese-nt in bothdrums and the size of the balls in the two drums is such that the grinding is progressively finer from one end of the air path to the other. General-- ly speaking, the effect of the mill 8 is to reduce by impact while the drum 14 ef- 'fects the final minute reduction by attrition.

There is also provided a free air path above the balls which provides an unobstructed course for such lparticles as may be reduced to final size at any point in the apparatus. This final size may be determined by properly controlling the air sup ply. The auxiliary air which enters around the deflector 13 is partially obstructed by a plate 25, as shown in Figure 3. This plate may -be rotated to any desired posi* tion by a handwheel `26. This'7 is desirable since the auxiliary air will take thepath ot least resistance land would normally travel through the upper half of the mill 14. The plate 25, however, closes off a portion of the space around the delector 13 and with the plate positioned as shown in Figure 1 most of the auxiliary air will travel through the lower half' of the drum. Since the coal vparticles tend to fall, it Will be seen that the auxiliary air will "pick up the` larger particles and materially assist in carrying them into the mill 14. If desired, the plate 25 may be made `smaller than the interior diameter ofthe air conduit at that point to provide apassage for a certain amount of air all around the opening 20 in order to better insure a complete air seal of the joint y23. The plate 25 may be rotated to shift the inlet of the auxiliary air as desired. f

In the embodiment of my invention shown in Figure-4, the materialis first ground in the outer drum 27 and then passes through the inner drum 28 for final reduction. In this view, lparts corresponding to similar parts in Figure 1 have been given the same reference characters with the suix a thereto.

A blower 27 may be provided if desired, and

either forced or induced draft alone, or both together, may be used, as desired, yto supply the conveying fluid. v

Figure 5 shows another form of drum corrugation which may be employed if desired.

It will be noted that a relatively 'high velocity is imparted to the air in all of the conduits. This serves to keep the, passages This same gradation is Cil clear and prevents any clogging therein. As soon, however, as the air reaches a grinding drum its velocity is immediately reduced to a great extent by the increase in cross-sectional area. The reduction in velocity immediately vresults in a deposition of the entrained, particles which are graded according to their mass. Both the inner and outer surfaces of the inside drum are utilized, particularly' the larger portion thereof.

This invention provides a pulverizer of high efficiency since the particles to be reduced are graded in accordance with the `gradations of the pulverizing system enabling every portion thereof to Work at maX- imum efficiency and resulting 1n a unlform product.

While l have illustrated the'preferred embodiment of -my invention, it will be understood that it is not limited thereto but may be embodied in other constructions within the scope of the following claims.'

l claim:

l. The method of pulverizing coal, which includes carrying coal through a pulverizing chamber by a fluid stream, substantially continuously varying the velocity of the fluid stream as it travels through the -pulverizing chamber, utilizing the stream tocarry the coal from the pulverizing chamber to a second Dulverizing chamber, and materially decreasing the velocity of the fluid as it passes into the second pulverizing chamber.

2. The method of pulverizing coal, which includes carrying coal through a pulverizing chamber by a fluid stream, utilizing.

the fluid stream to carry the coal from the pulverizino chamber to a second pulverizing chamber, materially decreasing the velocity of the fluid as it passes into the second pulverizing chamber, and substantially continuously varying the velocity of the fluid stream in at least one of the pulverizing chambers as it passes therethrough.

8. The method of pulverizing coal, which includescarrying coal through a pulverizing chamber by a fluid stream, utilizing the fluid stream to carry the coal from the pulverizing chamber to a second pulverizing chamber, introducing supplemental air between the pulverizing chambers, and materially decreasing the velocity of the fluid as it. passes into the second pulverizing chamber.

4. The method of pulverizing coal, which includes delivering the coal to a pulverizing chamber by a fluid stream, materially decreasing the velocity of the stream at a point in the pulverizer to deposit particles at a desired point, and substantially continuously varying the velocity of the stream as it passes through the pulverizer.

5. Pulverizing apparatus including a pulverizer, means for passmg a conveymg fluid therethrough, means forfeedmg maferial to the pulverizer, and auxiliary means for supplying conveying fluid at a point beyond that "where the original'fluid is supplied and adapted to convey material to another portion of the pulverizer substantially as described.

6. ilulverizing apparatus including a pulverizer, means for passing a conveying Huid therethrough, means for feeding material to the pulverizer, auxiliary means for supplying conveying fluid at a point beyond where the original fluid is supplied and adapted to convey material to another portion of the pulverizer, and means for adjusting the point of introduction of auxiliary duid, substantially as described.

7. Pulverizing apparatus including a plurality ofpulverizing mills, means for passing a conveying fluid through said mills, whereby `the material travels through the mills in succession, means for introducing auxiliary conveying fluid between mills, means for separately controlling said means, substantially as described.

8. Pulverizing apparatus including a plurality of pulverizing mills, means for passing a conveying fluid through the mills and means for varying the velocity of the conveying fluid as is passes through each of the mills, substantially as described.

9. Pulverizing apparatus, including a plurality of graded pulverizing mills, and means for passing a conveying fluid successively therethrough, each of the mills being so shaped as to vary the velocity of the conveying fluidas it passes therethrough and thus effect a corresponding gradation in the size of the particles deposited at different points through said graded pulverizing mills, substantially as described.

10. Pulverizing apparatus including a plurality of pulverizino mills, means for passing a conveying fluid through the mills, means for introducing auxiliary fluid between' the mills, means for maintaining a free fluid path through the mills, and means for shifting the inlet of the auxiliary fluid with respect to the free fluid path, substantially as described.

ll. Pulverizing apparatus including a mill having a plurality of rotary pulverizing chambers contained within one another, means for passing a conveying fluid through lll) the chambers in succession and means for introducing auxiliary fluid between the chambers, substantially as described.

12. Pulverizing apparatus including a pulverizer, means for passing a conveying fluid therethrough, means for feeding material to the pulverizer, auxiliary means for supplying conveying fluid at a point beyond that where the original fluid is supplied, and means for heating the medium, substantially 'as described.

13. Pulverizing apparatus including 4a mill having a plurality of pulverizing chambers, means for passing a conveying fluid through said chambers, whereby the material travels through the chambers in succession, means for introducing auxiliary conveying fluid between the chambers, and means for heating the medium, substantially as described.

14. Pulverizing apparatus including a plurality of pulverizing mills, means for passing a conveying fluid through the mills, means for varying the velocity of the conveying fluid as it passes through each of the mills, and means for heating the medium, substantially as described.

15. Pulverizing apparatus including a plurality of pulverizing mills, and means for passing a conveying-fluid through the mills, at least one of the mills having means for varying the velocity of the conveying 'fluid as it passes therethrough.

16. Pulverizing apparatus including a mill having a plurality of' rotary7 pulveri'zing chambers contained Within one another,

and means for passing a conveying fluid ing cross sectional area and each being provided with balls of different sizes.

19. In pulverizing apparatus, a rotary ball mill having a portion which is of di'- minishing cross sectional area, balls' of diiferent sizes within the mill, and means for passing a conveying Huid through the mill.

20. Pulverizing apparatus including two pulverizing chambers contained Within one another, and means for passing a conveying fluid through said chambers in succession, each of sa1d chambers constituting afluid path of dlmlnishlng cross-sectional area.

21. Pulverizing apparatus including a.

mill having a plurality of rotary pulverizing chambers contained Within one another, and means for passing a conveying fluid through said chambers in succession, each of said chambers having a conical portion the apexes of said portions being at opposite ends ofthe mill, the chambers providing a fluid path having a plurality of portions of diminishing cross-sectional area, substantiallyas described.

22. Pulverizing apparatus including a mill having a plurality of rotary pulverizing chambers contained Within one another, an means for passing a conveying fluid through said chambers in succession, each of said chambers being of diminishing cross sectional area, the diminution being in the direction of the fluid flow through such chamber, substantially as described.

23. Pulverizing apparatus including a mill having a plurality of rotary pulverizing chambers contained Within one another, each of said chambers being of diminishing cross-sectional area, the smaller ends ot the chambers being at opposite ends of the mill, and means4 for passing a conveying fluid from the larger to the smaller end of the chambers in succession.

24. Pulverizing apparatus including a mill having a plurality of substantially conical pulverizing chambers contained Within one another, the chambers being substantially coaxial and having their apex portions lying alternately at one end of the mill and the other, and means for passing a conveying fluid through said chambers'in succession.`

25. Pulverizing apparatus including a mill having a plurality of substantially conical pulverizing chambers contained Within one another, the chambers being substantially coaxial and having their apex portions lying alternately at one end of the mill and the other, and means for passing a. con'- veying fluid from the innermost to the outermost chamber in succession.

26. Pulverizing apparatus including a mill having a plurality of substantially conical pulverizing chambers contained Within one another, the chambers being substantially coaxial and having their apex portions lying alternately at one end of the mill and the other, and means for introducing conveying fluid at the base portion of one of the chambers and passing it to the apex portionof said chamber thence to the base portion of a succeeding chamber and through said chamber.

27. The method of pulverizing coal which includes passing a conveying Huid through a pulverizing system, and alternately increasing and decreasing the velocity of the conveying fluid as. it passes therethrough, at least one of the changes in velocit-y being relatively gradual, substantially as described.

28. The method of pulverizing coal which includes passing a conveying fluld through a pulverizing system, and alternately increasing and decreasing the velocity ot the conveying fluid as it passes therethrough, the increases in velocity being gradual and the decreases in velocity being relatively sudden,

lsubstantially as described.

29. Pulverizing apparatus includin mill having a plurality of successive grinding means Aadapted to reduce the material particles produced by the grindin means, to successively smaller sizes, the mill having the mill having an outlet for the v uid and 10 an inlet for conveying fluid, and means for the pulverlzed material carried thereby and passing a conveying :fluid through the mill being Huid-tight between the inlet and the and successively past the pulverizing means, outlet, substantially as described.

the inill being adapted to provide a velocity In testimony whereof I have hereunto -set I of the iluid stream which increases -to cormy hand. n respond to the increased :fineness of the LOUIS DE MARKUS. 

